Typically in tube and profile rolling mills there are a number of rolls and pairs of rolls spaced longitudinally along a forming path, the rolls being shaped to form a tube or profile from an initially flat strip, as the strip passes along the mill. Each roll has its own gearbox set to a carefully calculated ratio and is driven from that gearbox by a driven shaft. Although at manufacture, the gear ratios and roll dimensions are precisely defined, in practice these calculations are frequently invalidated by variations in material thickness and wear on the rolls. The result is that very often only one pair of rolls is travelling at the material speed and other rolls are either being pushed or pulled along by the material. This action not only causes further wear but also leads to a substantial recirculation of energy within the unit making it inefficient and expensive to run. To date no economic solution to this problem has been discovered and indeed in many mills the drive from a number of rolls is simply disconnected because of this problem.
The lack of an adequate solution is particularly surprising in view of the fact that on a typical tube forming mill the refurbishing of worn rolls costs many thousands of dollars per annum quite apart from the expensive down-time which occurs during the replacement of the rollers.
It is an object of the present invention to mitigate many of these difficulties.